HIPPARCOS - Hipparcos Main Catalog

The Hipparcos and Tycho Catalogues are the primary products of the
European Space Agency's astrometric mission, Hipparcos. The satellite,
which operated for four years, returned high quality scientific data
from November 1989 to March 1993.

Each of the catalogues contains a large quantity of very high quality
astrometric and photometric data. In addition there are associated
annexes featuring variability and double/multiple star data, and solar
system astrometric and photometric measurements. In the case of the
Hipparcos Catalogue, the principal parts are provided in both printed
and machine-readable form (on CDROM). In the case of the Tycho
Catalogue, results are provided in machine-readable form only (on
CDROM). Although in general only the final reduced and calibrated
astrometric and photometric data are provided, some auxiliary files
containing results from intermediate stages of the data processing, of
relevance for the more-specialised user, have also been retained for
publication. (Some, but not all, data files are available from the
Centre de Donnees astronomiques de Strasbourg.)

The global data analysis tasks, proceeding from nearly 1000 Gbit of
raw satellite data to the final catalogues, was a lengthy and complex
process, and was undertaken by the NDAC and FAST Consortia, together
responsible for the production of the Hipparcos Catalogue, and the
Tycho Consortium, responsible for the production of the Tycho
Catalogue. A fourth scientific consortium, the INCA Consortium, was
responsible for the construction of the Hipparcos observing programme,
compiling the best-available data for the selected stars before launch
into the Hipparcos Input Catalogue. The production of the Hipparcos
and Tycho Catalogues marks the formal end of the involvement in the
mission by the European Space Agency and the four scientific
consortia.

This database table was created by the HEASARC in April 2000 based on CDS
Catalog I/239/hip_main: the Hipparcos Main Catalog. It was updated in October
2002 to fix some entries which were missing coordinates.

Name
Name of the star in the recommended format for Hipparcos stars, as
created by concatenating the prefix 'HIP ' and the Hip_Number identifier in
the original catalog. Entries in the Hipparcos (HIP) Catalog have exactly the
same identifier as in the Hipparcos Input Catalog (HIC), notice.

RA
Right ascension in the specified equinox for epoch J1991.25. This
was given in the ICRS reference system (J2000 equator) in the original
Hipparcos Catalog, and thus equinox 2000 should be specified to avoid
inaccuracies due to the non-rigorous HEASARC coordinate precession algorithm.
This parameter was given to a truncated precision of 0.01 seconds of time in
the original Hipparcos Catalog. If the 'precise' RA is desired, one should
use the value of the parameter RA_deg which contains the complete RA in
decimal degrees.

Dec
Declination in specified equinox for epoch J1991.25. This
was given in the ICRS reference system (J2000 equator) in the original
Hipparcos Catalog, and thus equinox 2000 should be specified to avoid
inaccuracies due to the non-rigorous HEASARC coordinate precession algorithm.
This parameter was given to a truncated precision of 0.1 arcseconds in the
original Hipparcos Catalog. If the 'precise' declination is desired, one
should use the value of the parameter Dec_deg which contains the complete
declination in decimal degrees.

HIP_Number
The Hipparcos Catalog running number, which is the same as the
that in the Hipparcos Input Catalog. The star entries are, with a few
exceptions, ordered by increasing HIP number, which basically follows the
order of the object's right ascension (Equinox J2000) independent of
declination.

Prox_10asec
A proximity flag which provides a coarse indication of the
presence of nearby objects within 10 arcseconds of the position of the
given star. If non-blank, it indicates that there are one or more distinct
Hipparcos ('H') or Tycho ('T') Catalog entries; if both 'H' and 'T' apply,
then 'H' is the adopted value, notice.

Vmag
The magnitude in Johnson V band, given to a precision of 0.01 magnitudes
in the original Hipparcos Catalog.

Var_Flag
A coarse variability flag which indicates if the entry (or one
of the components in the case of a multiple system) is variable in its
Hipparcos magnitude Hip_mag at the level of:

G: ground-based multicolor photometry, either directly in or
reduced to the Johnson UBV system
H: Hipparcos magnitude Hip_mag, combined with information on the
color index (either V-I or BT_mag-VT_mag), in combination with
the luminosoty class
T: Tycho photometry, i.e., VT_mag and BT_mag-VT_mag
: no data available

RA_Deg
The right ascension expressed in degrees for epoch J1991.25
(JD2448349.0625 (TT)) in the ICRS (International Celestial Reference System,
consistent with J2000) reference system, and given to a precision of 10-8
degrees in the original Hipparcos Catalog. There are 263 cases where these
fields are missing (no astrometric solution could be found).

Dec_Deg
The declination expressed in degrees for epoch J1991.25
(JD2448349.0625 (TT)) in the ICRS (International Celestial Reference System,
consistent with J2000) reference system, and given to a precision of 10-8
degrees in the original Hipparcos Catalog. There are 263 cases where these
fields are missing (no astrometric solution could be found)

Astrom_Ref_Dbl
Reference flag for astrometric parameters of double and
multiple systems. This flag indicates that the astrometric parameters
refer to:

A, B etc: the letter indicates the specified component of a double
or multiple system
*: the photocentre of a double or multiple system included in
Part C of the Double and Multiple Systems Annex
+: the centre of mass: for such an entry, an orbit is given in
Part O of the Double and Multiple Systems Annex

Parallax
The trigonometric parallax pi in units of milliarcseconds: thus
to calculate the distance D in parsecs, D = 1000/pi. The estimated parallax
is given for every star, even if it appears to be insignificant or negative.

PM_RA
The proper motion component in the RA direction expressed in
milliarcseconds per Julian year (mas/yr), and given with respect to the
ICRS reference system: mu_RA* = mu_RA x cos (declination).

PM_Dec
The proper motion component in the declination direction expressed
in milliarcseconds per Julian year (mas/yr), and given with respect to the
ICRS reference system.

RA_Error
The standard error in the Right Ascension given at the
catalog epoch, J1991.25, and expressed in milliarcseconds:
sigma_RA* = sigma_RA x cos (declination).

Dec_Error
The standard error in the declination given at the
catalog epoch, J1991.25, and expressed in milliarcseconds.

Parallax_Error
The standard error in the parallax
given in milliarcseconds.

PM_RA_Error
The standard error in the proper motion component in the RA
direction expressed in milliarcseconds per Julian year (mas/yr):
sigma_mu_RA* = sigma_mu_RA x cos (declination).

PM_Dec_Error
The standard error in the proper motion component in the
declination direction expressed in milliarcseconds per Julian year (mas/yr),
sigma_mu_declination.

Crl_Dec_RA
The correlation coefficient expressed as a real numerical
value (in the printed catalog this is expressed in per cent, notice):
(declination over RA).

Crl_Plx_RA
The correlation coefficient expressed as a real numerical
value (in the printed catalog this is expressed in per cent, notice):
(parallax over RA).

Crl_Plx_Dec
The correlation coefficient expressed as a real numerical
value (in the printed catalog this is expressed in per cent, notice):
(parallax over declination).

Crl_Pmra_RA
The correlation coefficient expressed as a real numerical
value (in the printed catalog this is expressed in per cent, notice):
(proper motion in RA over RA).

Crl_Pmra_Dec
The correlation coefficient expressed as a real numerical
value (in the printed catalog this is expressed in per cent, notice):
(proper motion in RA over declination).

Crl_Pmra_Plx
The correlation coefficient expressed as a real numerical
value (in the printed catalog this is expressed in per cent, notice):
(proper motion in RA over parallax).

Crl_Pmdec_RA
The correlation coefficient expressed as a real numerical
value (in the printed catalog this is expressed in per cent, notice):
(proper motion in declination over RA).

Crl_Pmdec_Dec
The correlation coefficient expressed as a real numerical
value (in the printed catalog this is expressed in per cent, notice):
(proper motion in declination over declination).

Crl_Pmdec_Plx
The correlation coefficient expressed as a real numerical
value (in the printed catalog this is expressed in per cent, notice):
(proper motion in declination over parallax).

Crl_Pmdec_Pmra
The correlation coefficient expressed as a real numerical
value (in the printed catalog this is expressed in per cent, notice):
(proper motion in declination over proper motion in RA).

Reject_Percent
The percentage of data that had to be rejected in order
to obtain an acceptable solution.

Quality_Fit
The goodness-of-fit statistic: this number indicates the
goodness of fit of the astrometric solution to the accepted data (i.e.,
excluding the rejected data). For good fits, this should approximately
follow a normal distribution with zero mean value and unit standard
deviation. Values exceeding, say +3, thus indicate a bad fit to the data.

BT_Mag_Ref_Dbl
a reference flag for BT_mag and VT_mag which indicates,
for non-single stars, the component measured in Tycho photometry, or
indicates that several components have been directly measured together
by Tycho, or have had their Tycho data combined. The flag takes the
following values:

A, B, etc. : the Tycho photometry refers to the designated Hipparcos
Catalog component
* : the Tycho photometry refers to all components of the
relevant Hipparcos entry
- : the Tycho photometry refers to a single-pointing triple or
quadruple system, for which only a close pair has been
observed by Tycho, the other components being too faint
to be detected by Tycho

Mag_Ref_Dbl
A reference flag for the (B-V) and (V-I) color indices
and the V magnitude Vmag (and all their standard errors) which is set
to '*' when they refer to the combined light of double or multiple
systems which are otherwise resolved by the main mission astrometry
and photometry.

HIP_Mag
The median magnitude H_P in the Hipparcos photometric system,
and defined on the basis of the accepted observations (or field transits)
for a given star. Note that the Hipparcos magnitude could not be determined
for 14 stars.

N_Obs_HIP_Mag
The number of H_P observations: this is the number of
photometric observations (or field transits) used for the construction
of the median, standard error, and scatter in H_P.

HIP_Mag_Ref_Dbl
A reference flag for the Hipparcos photometric
parameters. For a double or multiple entry, this flag indicates that the
photometry refers to:

A, B, etc. : the specified component of a double or multiple system
* : combined photometry of a double system, corrected for
attenuation by the detector's instantaneous field of view
profile response
- : combined photometry of a double system, NOT corrected for
attenuation by the detector's instantaneous field of view
profile response

HIP_Mag_Max
The observed magnitude at maximum luminosity. This is
defined as the 5th percentile of the epoch photometry.

HIP_Mag_Min
The observed magnitude at minimum luminosity. This is
defined as the 95th percentile of the epoch photometry.

Var_Period
The variability period, or a provisional estimate of such
a period, derived on the basis of the Hipparcos data (possibly in
combination with ground-based observations) and expressed in days,
with a precision of 0.01 days.

HIP_Var_Type
The variability type: the sources of scatter in the
photometric data are various, and this flag indicates the origin of
the extra scatter, which may be astrophysical, or, in some cases,
instrumental. See Section 1.3, Appendix 2 of the published Hipparcos
Catalog for a more detailed description. Amongst astrophysical sources
of variability, this parameter only distinguishes between 'M'
(micro-variables), 'P' (periodic variables), and 'U' (unsolved
variables). Further variability details for the periodic or unsolved
variables are included in the Variability Annex. The flag takes the
following values:

C : no variability detected ("constant")
D : duplicity-induced variability
M : possibly micro-variable, with amplitude < 0.03 mag (stars
classified with high confidence as micro-variable are flagged U)
P : periodic variable
R : the V-I colour index was revised during the variability analysis
U : unsolved variable which does not fall in the other categories;
this class also includes irregular or semi-regular variables,
and possibly varaibles with amplitude > or ~ 0.03 mag
: a blank indicates that the entry could not be classified as
variable or constant with any degree of certainty

Var_Data_Annex
A Variability Annex flag indicating the existence of
additional tabular data in the Variability Annex, where '1' means that
additional data are provided in a table of periodic variables, and '2'
means that additional data are provided in a table of 'unsolved' variables.

Var_Curv_Annex
A Variability Annex flag indicating the existence of a
light curve, or a folded light curve, in the Variability Annex, where
'A' means the light curve is folded, and 'B' or 'C' mean that the
light curve is NOT folded.

CCDM_ID
The Catalog of Components of Double and Multiple Stars (CCDM)
identifier.

CCDM_History
The historical status of the CCDM identifier.
The flag takes the following values:

H : system determined as double or multiple by the Hipparcos
observations, and was previously unknown as double or multiple
I : system previously identified as multiple, as given in Annex 1
of the Hipparcos Input Catalog (HIC)
M : miscellaneous (system had been previously identified, after
publication of the HIC, using other more recently available
catalogs and compilations)

CCDM_N_Entries
The number of separate catalog entries with the same
CCDM identifier.

CCDM_N_Comp
The number of components into which the entry was
resolved as a result of the satellite observations and data reductions.

Dbl_Mult_Annex
The Double and Multiple Systems Annex flag. This
indicates that further details of this system are given in one of the 5
(mutually exclusive) parts of the Double and Multiple Systems Annex
labelled as follows:

Astrom_Mult_Source
A flag for the source of the absolute astrometry.
This parameter qualifies the source of the astrometric parameters for
some of the entries with a value of 'C' for the parameter Dbl_Mult_Annex.
The values are as follows:

P : primary target of a 2- or 3-pointing system
F : secondary or tertiary of a 2- or 3-pointing 'fixed' system
(common parallax and proper motions)
I : secondary or tertiary of a 2- or 3-pointing 'independent'
system (no constraints on parallax or proper motions)
L : secondary or tertiary of a 2- or 3-pointing 'linear' system
(common parallax)
S : astrometric parameters from 'single-star merging' process.

Dbl_Soln_Qual
A solution quality flag which indicates the reliability
of the double or multiple star solution, and is set for all entries in
Part C of the Double and Multiple Systems Annex. The flags can be
understood as follows:

Dbl_Ref_ID
Component designation for the double star parameters,
Dbl_theta, dbl_rho, etc. The first letter gives the 'reference' component,
and the second letter gives the subsidiary component. In the case of the
Hipparcos observations, the reference component is always defined to be
the brighter component (in median H_P) such that the magnitude difference
between the components (Diff_Hip_Mag) is always positive.

Dbl_Theta
The rounded value for the position angle between the components
specified in the Dbl_Ref_id field, expressed in degrees (in the usual
sense measured counterclockwise from North).

Dbl_Rho
The rounded value for the angular separation between the
components specified in the Dbl_Ref_id field, expressed in arcseconds.

Rho_Error
The standard error of the angular separation, Dbl_Rho,
given in arcseconds.

Diff_HIP_Mag
The Hipparcos magnitude difference of the components
specified in the Dbl_Ref_id field, expressed in magnitudes.

Dhip_Mag_Error
The standard error of the Hipparcos magnitude difference,
expressed in magnitudes.

Survey_Star
A flag indicating a `survey' star. The `survey' was the
basic list of bright stars added to and merged with the total list of
proposed stars, to provide a stellar sample (almost) complete to
well-defined limits. A flag 'S' indicates that the entry is contained
within this `survey', whose limiting magnitude is a function of the
stars's spectral type and galactic latitude b and is defined by:

If no spectral data were available, the break was taken at (B-V) = 0.8
mag.

ID_Chart
A flag indicating an identification chart. Where identification
of a star using ground-based telescopes might prove difficult or
ambiguous, identification chrats were constructed and are available
in Volume 13 of the printed catalog. Charts correspond to the object
observed by the satellite (i.e., at the posotion given in this catalog),
even if it was not the intended target. The flag takes the following
values: 'D' for charts produced directly from the STScI Digitized Sky
Survey (776 entries) or 'G' for charts constructed from the Guide Star
Catalog (10877 entries).

Notes
A flag indicating a note is given at the end of the volume(s)
in the printed catalog. The flag has the following meaning:

BD_ID
Bonner Durchmusterung (BD) identifier (CDS Catalogs <I 119>,
<I 122>). BD identifiers, unlike the CoD and CPD identifiers, may carry
a suffix letter for additional stars, i.e., stars with suffixes 'A',
"B', 'P', or 'S': these stars were added to the BD Catalog after the
original numbering was made, and such suffixes do not imply that the
entry is a component of a double or multiple system.